1. Field of Invention
This invention relates to respiratory protective systems, and more particularly to an advanced protective respiratory hood for protecting a wearer from contaminants including, but not limited to nuclear, chemical, biological, smoke and dust.
2. Background of the Invention
Devices that clean the air as it is drawn or forced through one or more filters are known as air purifying respirators (herein xe2x80x9cAPRsxe2x80x9d). Standard APRs utilize a negative pressure system in which contaminated air is pulled through a filter upon inhalation, allowing the wearer to breathe clean, filtered air. A full-face mask pertains to protective masks which protect the wearer""s eyes, face, and lungs from contamination. A half-face mask or half-mask does not protect the eyes, upper face and forehead. Rather, it is generally known in the art as a triangular-shaped cup that covers the mouth and nose of the wearer. Chemical resistant hoods protect the wearer against chemical agents such as xe2x80x9cliquid mustardxe2x80x9d which can cause severe burns to the head and neck. Hooded respirators are generally secured around the circumference of the neck and benefit from enhanced protection of the head area.
Military organizations, such as the U.S. Army, consistently place a number of objectives high on their list for respiratory protective devices. With soldiers carrying more equipment, there is an emphasis on reducing weight and bulk whenever possible. While full-face masks provide good protection to the wearer, they are difficult to compactly store and transport. Half-mask designs are more compact, but they do not protect the eyes, ears and head of the wearer from airborne contaminants.
Another need in both military and non-military operations is excellent outward visibility. Masks and hoods that fog due to accumulation of carbon dioxide and moisture from exhaled air severely inhibit a solider from successfully completing his mission. Furthermore, many designs have filters and other structures that encumber a soldier""s ability to sight a weapon or which may be snagged on other equipment.
Another need exists for a mask or hood that remains engaged during sudden movement. A number of designs, particularly those with a single filter, are subject to substantial torque when a wearer moves his head suddenly because the mass of the device is not equally distributed about the axis of the rotation for the wearer. This can cause the protective seal of the device to become disengaged, and thus the protection factor is compromised.
Another need exists for a device that uses readily available filtration media. Many designs in the prior art utilize proprietary filters which are solely intended to operate with a single design of respiratory protective device. This increases the manufacturing, quality control and inventory overhead for supporting the devices.
Another need exists for a protective hood respirator with improved verbal communication. Mouth-piece respirators are generally not acceptable where verbal communication is required as the mouth-piece must be disengaged to speak. Half-mask and full-face masks do permit verbal communication as they generally employ a cup that surrounds the mouth and nose.
Accordingly, what is needed in the art is a respiratory device that stores in a compact unit, provides substantially fog-free, unencumbered outward visibility, is stable and stays engaged to the wearer, even during violent movements, utilizes off-the-shelf filtration media, and provides verbal and drinking capability.
It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed.
However, in view of the prior art in at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified needs could be fulfilled.
The present invention comprises protective respiratory apparatus having a neck-sealable hood adapted to enclose the head of a wearer, the hood having an interior and an exterior. It is preferred that the hood be constructed of an elastomeric material such as butyl rubber or neoprene. Although fabric-type materials have been successfully employed in protective hoods in the past, elastomeric material is substantially quieter which may be particularly critical in military and law enforcement operations.
At least one filter is sealingly secured to the hood wherein air passing from the outside of the hood to the inside of the hood is filtered of contaminants. However, it is preferred that two filters be employed in symmetrical relation to the hood, and more specifically in the area proximate to the location of the wearer""s mouth and nose would be. The dual filter design has a number of advantages which include better outward vision in comparison to large, bulky center-mounted filters, lower breathing resistance, and better distribution of mass wherein less torque is suffered from sudden head movements due to the more equal distribution of weight. Still another advantage of the dual filter design is its ability to compact in tight relation, particularly when used with a flexible hood and half-mask.
The filters are sealed to the hood about the periphery of the filters. In one embodiment of the invention, the filters are fitted substantially flush with the exterior of the hood. The advantage to this configuration is that the bodies of the filters do not interfere with the operations of the wearer or get snagged on other equipment.
A half-mask cup adapted to sealingly cover the nose and mouth of the wearer is positioned inside the hood. The half-mask cup is mechanically, but not fluidly coupled to the filters. Accordingly, filtered air is not immediately drawn into the half-mask cup, but into the interior of the hood. It should be noted that while the half-mask cup is a preferred breathing interface for the invention, additional breathing interfaces may also be employed including, but not limited to, full-face masks and mouth-piece interfaces. A coupling part interconnects the filter to the half mask cup, the coupling part being imperforate so that it is impervious to fluid flow. A filtration part of the filter is pervious to fluid flow and is disposed radially outward from the coupling part. The fluid flow follows a path of travel through the filtration part, into the interior of the hood, flowing over the visor and into the half mask cup. The filter is therefore understood to be mechanically coupled to the half mask cup and fluidly coupled to the interior of the hood.
At least one air intake valve is integrated in the cup wherein filtered air resident in the interior of the hood is drawn into the half-mask cup for respiration by the wearer. A flexible and substantially transparent visor, preferably constructed of flexible urethane, is sealingly engaged to the hood and adapted to provide outward vision for the wearer. Preferably, the at least one air intake valve in the cup is located proximate to the nose bridge of the wearer whereby filtered air resident in the interior of the hood is drawn across the visor and into the at least one air intake valve responsive to inhalation by the wearer. The advantage of this configuration is that carbon dioxide and humidity, the primary culprits in visor fogging, are substantially reduced or eliminated by the air flow path across the visor.
In another embodiment of the invention, the hood includes at least one convexity disposed in outward relation from the interior of the hood analogous to a finger on a glove. The convexity has an axis of symmetry substantially similar to an individual filter. An aperture coincident with the axis of symmetry slideably receives and secures a filter by compressive interference fit. It is worthy to note this advancement over the prior art wherein past apertures were simply formed by a die cut on a two-dimensional plane. By forming the finger-like projection, the surface area seal between the elastomeric hood and the filter is overwhelmingly increased with a substantial benefit in the overall protection factor of the device. An alternative to this embodiment is to employ a concavity disposed in inward relation to the interior of the hood rather than a convexity disposed in outward relation.
In a preferred embodiment of the invention, a filter interface is sealingly attached about its periphery to the hood and substantially rigidly secured to the cup. The filter interface is adapted to screw threadably receive the at least one filter. An elastomeric gasket is sandwiched between the filter interface and the at least one filter to further provide a fluid-tight seal. An advantage of creating a filter interface is that the at least one filter is user-replaceable and the entire system lends itself to re-use and decontamination.
Alternatively, the at least one filter is slideably received by the filter interface and fluidly secured by a retention grill screw threadably received by the filter interface, the retention grill adapted to retain the at least one filter in sealing engagement with the filter interface. A visual indicator is provided to show when a complete engagement of the retention grill to the filter interface has been achieved. Preferably, the retention grill is provided in a binary engagement wherein it is clearly engaged or disengaged in Boolean relationxe2x80x94unlike a screw of a filter that has an infinite number of positions, some of which may allow for leakage between the screw threads.
The filter interface may further comprise flanges about its periphery which are sonically welded to the hood. In yet another embodiment of the filter interface may comprise a two-piece configuration, an inner portion substantially rigidly secured to the cup in the interior of the hood and an outer portion positioned in mirrored relation to the inner portion whereby the inner and outer portion are sonically welded together about their peripheries, sandwiching at least a portion of the hood therebetween to form a fluid-tight seal.
It should be noted that in a preferred embodiment of the invention the mechanical coupling of the cup to the at least one filter is fluid-tight. However, the present invention anticipates an embodiment wherein the mechanical coupling of the cup to the at least one filter is adapted to permit partial flow of air from the filter into the cup and partial flow of air from the filter into the interior of the hood. An alternative embodiment of the invention may include a split-flow configuration wherein at least one secondary filter is dedicated to full or partial fluid communication with the cup.
For extended wear in hazardous conditions, a conduit from the exterior of the hood into the cup may be provided whereby the wearer can drink fluids without removing the hood. Furthermore, it is preferred that a tension strap substantially encircling the exterior of the hood and attached to the filters or other hard-point on the exterior of the hood be provided whereby the cup is biased against the face of the wearer. Alternatively, the tension strap may be positioned in the interior of the hood.
It is important to remain cognizant that, without proper design features, unfiltered air may be introduced into the cup through the exhalation pathway. Accordingly, a preferred embodiment of the invention includes an exhalation valve mated to the cup, a baffling means in fluid communication with the exhalation valve wherein exhaled air exits the cup through the exhalation valve, through the baffling means and out into the atmosphere. The baffling means provides a buffer quantity of filtered, exhaled air as a protective barrier against unfiltered air. It is also preferred that the air intake valve and the exhalation valve be constructed as one-way check valves. To provide replacement functionality for the filters, it is preferred that they are screwably coupled to the cup, but still not fluidly coupled as that would defeat the anti-fog objectives of the air pathway.
In order to provide the optimum integration between hood and filter, a method of fabricated the hood is provided which includes the steps of forming an elastomeric hood by a dipping process having at least one convexity having an axis of symmetry, cutting at least one aperture coincident with the axis of symmetry and securing a filter by compressive interference fit within the aperture. It is advantageous to predetermine the circumference of the filters and cut the apertures to a circumference smaller than the circumference of the filters. This insures the tight, compressive fit between hood and filters. It is also preferred that the dipping process include pre-molding outline ridges of the visor, the apertures and the exhalation valve opening wherein die cutting along the outline ridges provides a substantially more efficient and precise assembly.
An advantage of the present invention is that the combination of half-mask, hood and dual filters permits the overall unit to be tightly packaged in a compact container. The half-mask is typically constructed of a resilient, elastomeric material which bends to move the filters in mirrored relation to each other. The flexible hood and visor then wraps around the half-mask and filters to form a compact design for storage, transport and carry.
An advantage of the half-mask configuration over mouth-sealable devices is that it permits better verbal communication and drink capability. Mouth-sealable devices, while enjoying a high protection factor, have limited wear times as wearers must disengage the mouth seal to drink liquids. In addition, verbal communication cannot be initiated without disengaging the mouth seal and, thus, diminishing the protection factor afforded by the mouth seal.
Still another advantage of the present invention is that inhaled air, previously flowing from the filter to the half-mask in the prior air, now flows into the hood first, passes over the transparent visor, then flows into the half-mask for respiration.
Still another advantage of the present invention is that convexities in the hood provide a tight, finger-like seal for the filters. Rather than simply sealing to the protective hood on a single plane, the filters are compressively engaged by an interference fit in three dimensions with a much greater surface area in contact than known in the prior art.
It is to be understood that both the foregoing general description and the following detailed description are explanatory and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute part of the specification, illustrate embodiments of the present invention and together with the general description, serve to explain principles of the present invention.
These and other important objects, advantages, and features of the invention will become clear as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims.